Age-Dependent Response of Hippocampal Neurons to Stress Age remains the most significant unexplained etiologic factor in common neurodegenerative diseases. To explore the basis of age-related sensitivity to common stressors, Ab and glutamate, we have developed novel techniques for isolation and culture of hippocampal rat neurons of any age (Brewer, 1997). Compared to embryonic and middle age neurons, we find that old neurons are more sensitive to glutamate and Ab toxicity (Brewer, 1998). Part of the mechanism involves age-related increases in apoptosis, indicated by more condensed nuclei and higher levels of caspase-3 activation. Here, we will test the hypothesis that age-related functional deficits in hippocampal mitochondria are responsible for age-related neurotoxicity of Ab and glutamate. Our aims will continue to use hippocampal neurons isolated from rat brains of three ages embryonic, middle and old age) to compare single cell function under uniform culture conditions: 1) Are age related functional deficits of mitochondria responsible for the age-related increase in susceptibility to glutamate and A-beta stressors? Mitochondrial deficits will be measured as respiration, steps in oxidative phosphorylation, preconditioning, release of cytochrome C and oxyradical products. 2) Can multiple inhibitor: better protect against age-related stressor toxicity than either alone? 3) Are there age-related deficits in mitochondrial DNA of mice transgenic for mutant human APP in situ hybridization with probes for common deletions? 4) Can neuron multiplication select for wild-type mitochondrial DNA and thereby restore normal function including response to stressors? These studies are likely to reveal mechanistic insights into age related neurotoxicity and suggest new targets for therapeutic intervention at both preventative and restorative levels of neurodegeneration.